Spiral Geometry Research Articles

Numerical Performance Analysis of Modified Vertical U-tube Ground Heat Exchangers by Adjusting the Impact of Leg Spacing

Geothermal energy is a reliable and renewable form of energy that offers steady cooling and heating of buildings without relying on sunlight or wind, avoiding price fluctuations. Ground heat exchangers (GHEs) are designed to utilize geothermal energy for building heating and cooling. The present study conducted a numerical investigation on the thermal performance of Modified Vertical U-tube GHEs. Enhancement of the thermal performance of various configurations of GHEs by adjusting the leg spacing and incorporating spiral configuration of U-tube GHEs. The upper section's leg spacing varies to reduce thermal interference and the lower section's leg spacing is kept constant. Some designs incorporated a combination of spiral and straight U-tubes. All GHE models were considered a 20-meter depth. Performances of these GHEs are evaluated with polyethylene, high-density polyethylene, and low-density polyethylene tubes and boreholes filled with silica sand. The surrounding soil consisted of clay. In some configurations, the lower section was modeled with spiral geometry after 10 meters in depth. The design parameters for the spiral section were 70 mm and 100 mm diameter. The simulations were conducted using the ANSYS FLUENT 22.2 software program for cooling operation. The outlet temperature was lower for spiral configurations than for the other configurations after being simulated for 72 hours. Compared to the traditional U-tube configuration, the heat transfer rate achieved by each arrangement is significantly higher. Results indicated that the combination of spiral shape with traditional shape led to a 31.2% increase in average heat transfer rate. Leg spacing variation opens up the opportunity to combine multiple geometries in a single borehole, also providing the solution to reduce the thermal interference between the inlet and outlet pipe.

Cross-Domain Denoising for Low-Dose Multi-Frame Spiral Computed Tomography.

Computed tomography (CT) has been used worldwide as a non-invasive test to assist in diagnosis. However, the ionizing nature of X-ray exposure raises concerns about potential health risks such as cancer. The desire for lower radiation doses has driven researchers to improve reconstruction quality. Although previous studies on low-dose computed tomography (LDCT) denoising have demonstrated the effectiveness of learning-based methods, most were developed on the simulated data. However, the real-world scenario differs significantly from the simulation domain, especially when using the multi-slice spiral scanner geometry. This paper proposes a two-stage method for the commercially available multi-slice spiral CT scanners that better exploits the complete reconstruction pipeline for LDCT denoising across different domains. Our approach makes good use of the high redundancy of multi-slice projections and the volumetric reconstructions while leveraging the over-smoothing issue in conventional cascaded frameworks caused by aggressive denoising. The dedicated design also provides a more explicit interpretation of the data flow. Extensive experiments on various datasets showed that the proposed method could remove up to 70% of noise without compromised spatial resolution, while subjective evaluations by two experienced radiologists further supported its superior performance against state-of-the-art methods in clinical practice. Code is available at https://github.com/YCL92/TMD-LDCT.

Numerical study on heat transfer of two-phase fluid in helical coil pipe under ocean condition

The thermal hydraulic characteristics and heat transfer of two-phase fluid in helical coil once-through steam generator under ocean conditions like rolling and heaving motions are studied numerically. A CFD model is established to analyze the effects of motion parameters like amplitude, period and rolling radius and the heat flux distribution are discussed. The analysis shows that the overall heat transfer decreases under ocean conditions, but the overall deterioration is limited, indicting the helical coil pipe has the stability for ocean conditions. The additional forces like Coriolis, centrifugal and inertial forces introduced by rolling motion are analyzed theoretically and the result shows it detorts the original two main vortexes responsible for high heat transfer due to its spiral geometry, making heat transfer fluctuates up and down periodically near the steady state value. As rolling height increases, the heat transfer is nonlinear due to the competition between Coriolis force and centrifugal and inertial forces. As rolling amplitude increases, the heat transfer variation increases and the local heat transfer deterioration is severely aggravated, indicating high rolling amplitude should be avoided as possible. Increasing rolling period makes heat transfer behavior more approximate to static case as gravity and centrifugal force due to spiral geometry is dominate. Under heaving motion, the overall heat transfer decreases, and increasing heaving amplitude and decreasing period make the fluctuation more severe.

Hydrothermal behaviour of hybrid nanofluid flow in two types of shell and helical coil tube heat exchangers with a new design. Numerical approach

High-efficiency thermal energy systems are very important in meeting the growing demand for thermal energy. As a result, several heat transfer improvements have been proposed. Some promising methods include flow heat transfer in shell and spiral tube exchangers.In a shell-and-coil heat exchanger, utilizing a meticulously designed coil instead of a basic one significantly boosts heat transfer and overall thermal efficiency. This is due to the enhanced fluid dynamics and increased turbulence facilitated by the advanced coil design, making it ideal for space-constrained applications. Moreover, the helical configuration helps minimize fouling and maintenance, and may also provide self-cleaning benefits. Consequently, helical coils are highly regarded in industrial contexts for their superior performance, maintenance ease, and design adaptability.This study conducts a numerical evaluation of the heat transfer and fluid flow properties of two distinct shell-and-coil heat exchangers with specialized designs. The fluids analyzed include water-based hybrid nanofluids, specifically Water/MgO-TiO2and Ag-HEG/water, with results compared to those obtained using pure water. The investigation spans Reynolds numbers from 500 to 2000 and is divided into two segments.The first segment examines the influence of spiral coil geometry and fluid type on the heat exchanger's endothermic performance, utilizing nanoparticle volume concentrations of φ1 = φ2 = 0.3. In the second segment, the optimal geometric and fluid model is chosen based on the findings from the first part. Following this, the impact of various hybrid nanofluids on thermal performance is assessed, comparing fluids with volume concentrations of φ1 = φ2 = 0.3 to pure water (φ1 = φ2 = 0).The findings reveal that Case [A], featuring a unique geometry with Water/Ag_HEG, achieves the highest thermal performance across all examined Reynolds numbers. At the lowest Reynolds number, the thermal efficiency improvements for Case [A], Case [B], and Case [C] were 137 %, 113 %, and 56 %, respectively, compared to the baseline. Additionally, the second part of the study demonstrates that at the lowest Reynolds number, the thermal efficiencies of Water/MgO-TiO2 and Water/Ag_HEG nanohybrid fluids increased by 76 % and 49 %, respectively.

Lab-on-Chip Systems for Cell Sorting: Main Features and Advantages of Inertial Focusing in Spiral Microchannels.

Inertial focusing-based Lab-on-Chip systems represent a promising technology for cell sorting in various applications, thanks to their alignment with the ASSURED criteria recommended by the World Health Organization: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Delivered. Inertial focusing techniques using spiral microchannels offer a rapid, portable, and easy-to-prototype solution for cell sorting. Various microfluidic devices have been investigated in the literature to understand how hydrodynamic forces influence particle focusing in spiral microchannels. This is crucial for the effective prototyping of devices that allow for high-throughput and efficient filtration of particles of different sizes. However, a clear, comprehensive, and organized overview of current research in this area is lacking. This review aims to fill this gap by offering a thorough summary of the existing literature, thereby guiding future experimentation and facilitating the selection of spiral geometries and materials for cell sorting in microchannels. To this end, we begin with a detailed theoretical introduction to the physical mechanisms underlying particle separation in spiral microfluidic channels. We also dedicate a section to the materials and prototyping techniques most commonly used for spiral microchannels, highlighting and discussing their respective advantages and disadvantages. Subsequently, we provide a critical examination of the key details of inertial focusing across various cross-sections (rectangular, trapezoidal, triangular, hybrid) in spiral devices as reported in the literature.

Optimization of Nanowell-Based Label-Free Impedance Biosensor Based on Different Nanowell Structures.

Nanowell-based impedance-based label-free biosensors have demonstrated significant advantages in sensitivity, simplicity, and accuracy for detecting cancer biomarkers and macromolecules compared to conventional impedance-based biosensors. Although nanowell arrays have previously been employed for biomarker detection, a notable limitation exists in the photolithography step of their fabrication process, leading to a reduced efficiency rate. Historically, the diameter of these nanowells has been 2 μm. To address this issue, we propose alternative geometries for nanowells that feature larger surface areas while maintaining a similar circumference, thereby enhancing the fabrication efficiency of the biosensors. We investigated three geometries: tube, spiral, and quatrefoil. Impedance measurements of the samples were conducted at 10 min intervals using a lock-in amplifier. The study utilized interleukin-6 (IL-6) antibodies and antigens/proteins at a concentration of 100 nM as the target macromolecules. The results indicated that tube-shaped nanowells exhibited the highest sensitivity for detecting IL-6 protein, with an impedance change of 9.55%. In contrast, the spiral, quatrefoil, and circle geometries showed impedance changes of 0.91%, 0.95%, and 1.62%, respectively. Therefore, the tube-shaped nanowell structure presents a promising alternative to conventional nanowell arrays for future studies, potentially enhancing the efficiency and sensitivity of biosensor fabrication.

A Comparative Experimental Analysis of the Effect of Spiral Geometry on the Separation of Fine Chromite Particles. Part 1: Potential Downstream Impacts

A Comparative Experimental Analysis of the Effect of Spiral Geometry on the Separation of Fine Chromite Particles. Part 1: Potential Downstream Impacts

Investigation of process parameters of electrohydrodynamic jetting for 3D printed PCL fibrous scaffolds with complex geometries

Tissue engineering is a promising technology in the field of regenerative medicine with its potential to create tissues de novo. Though there has been a good progress in this field so far, there still exists the challenge of providing a 3D micro-architecture to the artificial tissue construct, to mimic the native cell or tissue environment. Both 3D printing and 3D bioprinting are looked upon as an excellent solution due to their capabilities of mimicking the native tissue architecture layer-by-layer with high precision and appreciable resolution. Electrohydrodynamic jetting (E-jetting) is one type of 3D printing, in which, a high electric voltage is applied between the extruding nozzle and the substrate in order to print highly controlled fibres. In this study, an E-jetting system was developed in-house for the purpose of 3D printing of fibrous scaffolds. The effect of various E-jetting parameters, namely the supply voltage, solution concentration, nozzle-to-substrate distance, stage (printing) speed and solution dispensing feed rate on the diameter of printed fibres were studied at the first stage. Optimized parameters were then used to print Polycaprolactone (PCL) scaffolds of highly complex geometries, i.e., semi-lunar and spiral geometries, with the aim of demonstrating the flexibility and capability of the system to fabricate complex geometry scaffolds and biomimic the complex 3D micro-architecture of native tissue environment. The spiral geometry is expected to result in better cell migration during cell culture and tissue maturation.

Improving the thermal performance of vertical ground heat exchanger by modifying spiral tube geometry: A numerical study

Ground heat exchanger (GHE) is the most crucial element of a ground source heat pump (GSHP) system for building cooling and heating by the utilization of geothermal energy. Therefore, intending to enhance the performance of GHE, the present study conducts a computational investigation of the thermal performance of modified spiral tube vertical GHEs. Several modifications of uniform-pitched spiral GHE are made to increase its thermal performance. Some modifications are introduced as variable-pitched spiral tube GHE where spiral inlet pipes are densified in the lower part of GHEs by reducing pitch distance. Conversely, in some modifications, the position of the outlet straight pipe is changed. Water is considered as the working fluid and the inlet temperature of the water is maintained fixed at 300.15 K. After extensive analysis, it is evident that, when the outlet pipe is placed outside of the spiral coil, there is a 7.67 % enhancement in the thermal performance than a traditional uniform-pitched spiral tube GHE. However, modifications like variable-pitched spiral tube GHEs are not significant to improve the thermal performance due to the quick saturation of the ground soil temperature around the GHE pipes. To have a balance between heat transfer rate and pressure drop, thermal performance capability (TPC) and coefficient of performance improvement (COPimprvt) criterion were evaluated and it is found that the uniform-pitched spiral tube GHE along with the outlet pipe at the outside of the spiral provides maximum thermal performance with a maximum TPC value of 1.062 and provides the positive value of COPimprvt criterion. The positive values of COPimprvt indicate that the spiral tube GHEs are energy efficient based on heat transfer and pressure drop. Moreover, spiral GHE with high-density polyethylene (HDPE), concrete pile, and sandy clay outperform the other materials for pipe, backfill, and soil, respectively. Specifically, HDPE pipe, concrete backfill, and sandy clay as soil offer around 7 %, 5 %, and 7.8 % higher thermal performance compared to polyethylene, sand silica, and clay, respectively.

Inertial particle focusing in fluid flow through spiral ducts: dynamics, tipping phenomena and particle separation

Small finite-size particles suspended in fluid flow through an enclosed curved duct can focus to points or periodic orbits in the two-dimensional duct cross-section. This particle focusing is due to a balance between inertial lift forces arising from axial flow and drag forces arising from cross-sectional vortices. The inertial particle focusing phenomenon has been exploited in various industrial and medical applications to passively separate particles by size using purely hydrodynamic effects. A fixed size particle in a circular duct with a uniform rectangular cross-section can have a variety of particle attractors, such as stable nodes/spirals or limit cycles, depending on the radius of curvature of the duct. Bifurcations occur at different radii of curvature, such as pitchfork, saddle-node and saddle-node infinite period (SNIPER), which result in variations in the location, number and nature of these particle attractors. By using a quasi-steady approximation, we extend the theoretical model of Harding et al. (J. Fluid Mech., vol. 875, 2019, pp. 1–43) developed for the particle dynamics in circular ducts to spiral duct geometries with slowly varying curvature, and numerically explore the particle dynamics within. Bifurcations of particle attractors with respect to radius of curvature can be traversed within spiral ducts and give rise to a rich nonlinear particle dynamics and various types of tipping phenomena, such as bifurcation-induced tipping (B-tipping), rate-induced tipping (R-tipping) and a combination of both, which we explore in detail. We discuss implications of these unsteady dynamical behaviours for particle separation and propose novel mechanisms to separate particles by size in a non-equilibrium manner.

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Seashell-inspired polarization-sensitive tonotopic metasensor

Bioinspiration has widely been demonstrated to be a powerful approach for the design of innovative structures and devices. Recently, this concept has been extended to the field of elasticity, dynamics, and metamaterials. In this paper, we propose a seashell-inspired metasensor that can simultaneously perform spatial frequency mapping and act as a polarizer. The structure emerges from a universal parametric design that encompasses diverse spiral geometries with varying circular cross sections and curvature radii, all leading to tonotopic behavior. Adoption of an optimization process leads to a planar geometry that enables us to simultaneously achieve tonotopy for orthogonally polarized modes, leading to the possibility to control polarization as well as the spatial distribution of frequency maxima along the spiral axis. We demonstrate the versatility of the device and discuss the possible applications in the field of acoustics and sensing.

Spiral bevel gears tooth geometry based on tooth trace and contact ellipse theory

Spiral bevel gears tooth geometry based on tooth trace and contact ellipse theory

Effect of humidification of combustion products in the boiler economizer with spiral geometry

In light of rising fuel prices and climate change in recent decades, improving the performance of heat recovery equipment such as boiler economizers is critical. Currently, numerical work is being done to improve the performance of the economizer with spiral geometry by humidifying combustion products. Simulations are performed using the finite volume method (FVM) and, in three cases, in a two-dimensional, steady, single-phase, and turbulent condition. In the first case, water vapor condensation and liquid water spray are not considered. In the second case, the impact of water vapor condensation is considered, and the effect of liquid water spray is not considered. In the third case, the water vapor condensation and the liquid water spray are simultaneously considered. Experimental correlation relations are used to predict the condensation rate in the second and third cases. The results are presented and discussed in the form of Nusselt number, convection heat transfer coefficient (h), outlet temperature, and heat transfer rate for different inlet temperatures of combustion products. Moreover, velocity, pressure, temperature contours, and velocity vectors are obtained and analyzed. The results showed that the cold-water outlet temperature in the third case was 2.85% higher than in the first case. In addition, a maximum improvement of 1.39% in the third case is obtained compared to the second case. Also, the heat transfer rate in the third case is improved by 8.2% compared to the first case and by 3.9% compared to the second case. The proposed method in the present work can be used to predict the effect of liquid water spray on the performance of boiler economizers.

Investigating the Linkage Between Spiral Trough Morphology and Cloud Coverage on the Martian North Polar Layered Deposits

AbstractThe martian North Polar layered deposits (NPLD) are composed of alternating water‐ice and dust‐rich layers resulting from atmospheric deposition and are key to understanding Mars climate cycles. Within these deposits are spiral troughs whose migration affects deposition signals. To understand the relationship between NPLD stratigraphy and Martian climate, we must identify modern‐day drivers of NPLD ice migration. Prevailing theory posits migration driven by upstream‐migrating bed undulations bounded by hydraulic jumps, caused by katabatic winds flowing over trough walls with asymmetric cross‐sectional relief. This is supported by trough‐parallel clouds, whose formation has been attributed to hydraulic jumps. We present a cloud atlas across the Martian north pole using ∼13,800 THEMIS images spanning ∼18 Earth years. We find trough‐parallel clouds in ∼400 images, with regions nearer to the pole having higher cloud frequency. We compare spiral trough geometry to our cloud atlas and find regions with trough‐parallel clouds often correlate with metrics associated with modern‐day sublimation‐deposition cycles (i.e., relief and asymmetry), but not always. In some regions, troughs with morphologies conducive to cloud formation have no clouds. Overall, trough geometry varies greatly across the deposits, both within and between troughs, suggesting localized differences in deposition relative to migration, varying katabatic wind intensities, differing past climatic states influencing the troughs, varying trough initiation properties, or the possibility of additional mechanisms for trough initiation and migration (e.g., in situ trough erosion). Understanding what controls trough shape variability across the NPLD and how these controls change through time and space is key when interpreting Martian paleoclimate.

Heliospheric Diffusion of Stochastic Parker Spirals in Radially Evolving Solar Wind Turbulence

We present a stochastic field line mapping model where the interplanetary magnetic field lines are described by a density distribution function satisfying a Fokker–Planck equation that is solved numerically. Due to the spiral geometry of the nominal Parker field and to the evolving nature of solar wind turbulence, the heliospheric diffusion of the magnetic field lines is both heterogeneous and anisotropic, including a radial component. The longitudinal distributions of the magnetic field lines are shown to be close to circular Gaussian distributions, although they develop a noticeable skewness. The magnetic field lines emanating from the Sun are found to differ, on average, from the spirals predicted by Parker. Although the spirals remain close to Archimedean, they are here underwound, on average. Our model predicts a spiral angle that is smaller by ∼5° than the Parker spiral angle at Earth’s orbit for the same solar wind speed of V sw = 400 km s−1. It also predicts an angular position on the solar disk of the best magnetically connected footpoint to an observer at 1 au that is shifted westward by ∼10° with respect to the Parker’s field model. This significantly changes the angle of the most probable magnetic connection between possible sources on the Sun and observers in the inner heliosphere. The results have direct implications for the heliospheric transport of “scatter-free” electrons accelerated in the aftermath of solar eruptions.

Acclimation of intertidally reproducing sea-snails protects embryos from lethal effects of transient hyperthermia.

Embryos of Ilyanassa obsoleta (from Massachusetts and Florida) and Phrontis vibex (from Florida) were exposed to temperatures from 33to 37°C. In both species, very young embryos are especially sensitive to thermal stress. Brief early heat shock did not disturb spiral cleavage geometry but led to variable, typically severe defects in larval morphogenesis and tissue differentiation. In Ilyanassa but not P. vibex, early heat shock resulted in immediate slowing or arrest of interphase progression during early cleavage. This reversible arrest was correlated with improved prognosis for larval development and (in Massachusetts snails, at least) depended on parental acclimation to warm temperature (~25.5°C). Embryos from Massachusetts snails housed at lower temperature (16°C) exhibited cytokinesis failure when briefly incubated at 33°C during early cleavage, and tissue differentiation failure during incubation at 33°C begun at later stages. This preliminary study reveals a case in which stress-conditioned parents may endow embryos with protection against potentially lethal thermal stress during the most vulnerable stages of life.

Twisted fiber microfluidics: a cutting-edge approach to 3D spiral devices.

The development of 3D spiral microfluidics has opened new avenues for leveraging inertial focusing to analyze small fluid volumes, thereby advancing research across chemical, physical, and biological disciplines. While traditional straight microchannels rely solely on inertial lift forces, the novel spiral geometry generates Dean drag forces, eliminating the necessity for external fields in fluid manipulation. Nevertheless, fabricating 3D spiral microfluidics remains a labor-intensive and costly endeavor, hindering its widespread adoption. Moreover, conventional lithographic methods primarily yield 2D planar devices, thereby limiting the selection of materials and geometrical configurations. To address these challenges, this work introduces a streamlined fabrication method for 3D spiral microfluidic devices, employing rotational force within a miniaturized thermal drawing process, termed as mini-rTDP. This innovation allows for rapid prototyping of twisted fiber-based microfluidics featuring versatility in material selection and heightened geometric intricacy. To validate the performance of these devices, we combined computational modeling with microtomographic particle image velocimetry (μTPIV) to comprehensively characterize the 3D flow dynamics. Our results corroborate the presence of a steady secondary flow, underscoring the effectiveness of our approach. Our 3D spiral microfluidics platform paves the way for exploring intricate microflow dynamics, with promising applications in areas such as drug delivery, diagnostics, and lab-on-a-chip systems.

Comparison of Coupled Electrochemical and Thermal Modelling Strategies of 18650 Li-Ion Batteries in Finite Element Analysis-A Review.

The specificities of temperature-dependent electrochemical modelling strategies of 18650 Li-ion batteries were investigated in pseudo-2D, 2D and 3D domains using finite element analysis. Emphasis was placed on exploring the challenges associated with the geometric representation of the batteries in each domain, as well as analysing the performance of coupled thermal-electrochemical models. The results of the simulations were compared with real reference measurements, where temperature data were collected using temperature sensors and a thermal camera. It was highlighted that the spiral geometry provides the most realistic results in terms of the temperature distribution, as its layered structure allows for a detailed realisation of the radial heat transfer within the cell. On the other hand, the 3D-lumped thermal model is able to recover the temperature distribution in the axial direction of the cell and to reveal the influence of the cell cap and the cell wall on the thermal behaviour of the cell. The effect of cooling is an important factor that can be introduced in the models as a boundary condition by heat convection or heat flux. It has been shown that both regulated and unregulated (i.e., natural) cooling conditions can be achieved using an appropriate choice of the rate and type of cooling applied.

Flyback Micro-Converter Design with an Integrated Octagonal Micro-Transformer for DC-DC Conversion

The work presented in this paper concerns the design of an integrated flyback DC-DC micro-converter operating at high frequencies. The flyback converter consists of only one transformer. The integrated micro-transformer in the flyback micro-converter is composed of two planar stacked coils with spiral octagonal geometry. Basing on Mohan’s method, the geometrical parameters are evaluated. The different parasitic effects created in the stacked layers are grouped perfectly in the equivalent electrical circuit that summarizes all parasitic effects. The integrated micro-transformer is characterized by scattering parameters extraction. The thermal and electromagnetic effects generated in the micro-transformer are illustrated, using finite elements method on COMSOL Multiphysics 5.3 software. To validate the electrical model, the simulation of the flyback micro-converter containing the equivalent electrical circuit of the micro-transformer is established, using PSIM 9.0 software. The gap between the coils is considered as an integrated MIM capacitor created at high frequencies leads to create a low pass micro-filter with the secondary coil.